


Fallen Under

by ArcticCalamity



Category: Undertale (Video Game)
Genre: Biting, Blood, Breathplay, Burns, F/M, Multi, Threesome, Underfell, underfrick
Language: English
Status: In-Progress
Published: 2015-12-07
Updated: 2015-12-07
Packaged: 2018-05-05 10:29:55
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 4,030
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/5372006
Author URL: https://archiveofourown.org/users/ArcticCalamity/pseuds/ArcticCalamity
Summary: <blockquote class="userstuff">
              <p>After falling into a world that seems out to kill you, you find you must rely on the mercy of monsters who might be the only chance you have to stay alive.</p><p>Based on the Underfell AU.</p>
            </blockquote>





	Fallen Under

**Author's Note:**

> boy oh boy just fuck me up
> 
> I'm a filthy sinner who wants to fuck the Underfell characters????????? im sorry
> 
> This is an of-age dfab reader with gender neutral pronouns. Sans says kiddo but its sans so
> 
> EDIT:: I swear to god I have multiple people read these stories and I still find missing words oops. My bad. I've fixed as many as I could find.

There were dozens of pairs of eyes on you as you sat at the bar. You picked up your drink and took a sip. It wasn’t alcoholic; you didn’t want to have your senses muddled while you were trapped in the underground. The monsters around you weren’t outright attacking, not in Grillby’s. They knew better. The bartender stood off to the side, idly wiping a glass with a cloth. He wasn’t looking at you, or at least you thought he wasn’t. There were no eyes set into the dark flames he called a body and only his glasses showed which direction he was casting whatever gaze he had. In this dark hell of a world, this bar was your only safe haven.

When you had first run into town, avoiding the vicious traps and attacks from the monsters in the forest, it was as though there was no end to the fear and torture. Everything had calmed down somewhat in the town, but people eyed you suspiciously, and the shop refused to serve you. The cavern was dark and snow was falling from some clouds that hung in the sky above you. You didn’t know how the cave could snow, but then again you also knew it was fruitless to question the logic of a world filled with magic and monsters. Your clothes were ripped and bloody, and the icy wind cut through you and left you shivering. By the time you had reached the end of the town you were exhausted, freezing, and your stomach was growling. Grillby’s had sat like a glowing beacon in the twilight, the warmth radiating from the building every time the door opened. You had feared the same persecution that the other monsters had shown you, but the owner of this place was different.

Grillby was tall and held himself with an air of self-assuredness. His suit was neat and clean despite being the only one who seemed to be making or serving any food. When you came in and sat down, he served you food and gave you a drink despite your humanity and bedraggled appearance. There was some kind of power that radiated from him, a strength that you weren’t sure a man made of fire could possess. Any time a monster tried to approach he would stare them down, making them give you a wide berth. It made you feel safe knowing he was keeping you from being harassed, but at the same time it scared you. After all, he was still a monster. Who knew what he could be capable of.

You took another sip of your drink, letting the warm liquid fill you up and soothe your chilled extremities. There was a plate of fries in front of you but you had barely touched them. You sighed. The air smelled like food and the sounds of people talking were comforting. In another place, this would be so normal, so routine, but surrounded by creatures that wanted to kill you, it was unnerving. You almost jumped when someone came and sat at the stool next to you. Your head whipped to the right, afraid someone had come to start a fight, but it was just the shorter skeleton you first encountered in the snowy wasteland. What was his name? Simon or Stan or something of the sort. He had introduced himself, but he and his brother were soon assaulting you with deadly gauntlets and you spent more time running for your life than socializing. You moved to the edge of your seat, giving the monster his space. He grabbed a bottle of mustard from the counter and stuck one end in his mouth. Your stomach turned as you watched him consume the condiment. He glanced over at you and flashed you a toothy grin, the gold standing out against the whiteness of his bones. You smiled back weakly, desperately hoping he didn’t have something treacherous planned for you. He didn’t seem to be one for doing work, though. That was mostly his brother.

“Hey there,” he said, not looking away. You averted your gaze, hoping that if you didn’t speak he would give up and forget you were there. You took a couple fries and ate them quickly. It helped a little to keep your mind and mouth distracted, but after a few more seconds you could still feel his eyes boring into you.

“It’s rude to ignore someone when they’re talking, y’know.” His voice sent shivers down your spine, but you weren’t quite sure why. You figured it had something to do with the fact that he could probably kill you with the flick of his wrist. You glanced over at him.

“What do you want?” you asked.

“You know if you want to hide from me and my brother you probably shouldn’t be hanging around where we live.”

“Oh yeah, well…” You paused for a moment, watching as he grinned condescendingly. “What makes you think I was trying to hide from you, anyway?”

“I dunno. Maybe it’s how you ran away screaming. ‘Help me! Save me!’ Pathetic.” He laughed and your face flushed. He had tried to kill you and now he was making fun of you for trying to save your own skin? You wanted to smack him or challenge him to a fight, and your eyes glared daggers at him. You knew better than to strike him, though.

“Sans. Leave my customer alone.” Grillby said as he returned to this side of the bar. His voice was stern and only a little angry, like a chastising father. Sans, that was his name. He huffed and rolled his eyes, focusing his attention on the mustard bottle he was still nursing.

“Grillbz what’re you doing serving this human, anyway?”

“They walked in here, so they’re my customer. Don’t test me.” His tone was clearly a warning, it was low and dangerous and punctuated with the crackling flames of his body. Sans scoffed.

“Yeah, whatever. My brother will just kill them as soon as they try to leave the city anyway.”

“Not if I keep them here.” Grillby said. Sans slammed the condiment down and glared at him.

“What?” he hissed. Your eyes shot to Grillby in shock.

“Excuse me?” you asked. Grillby pointedly ignored you, keeping his face pointed at Sans.

“You heard me. It’s been a while since I’ve had a pet. Maybe I’ll just keep them.”

“Why, you little…” Sans stood up. “What makes you think you get to keep them, huh? Why do you get dibs?”

“Neither of you get dibs! I’m not an object.” You insisted, standing up and stepping back from the counter. You were ready to run.

“Shut up.” Sans said. Grillby made a noise that almost sounded like a growl and grabbed the skeleton by the front of his shirt. A red glow started in Sans’ left eye and a heavy pressure filled the room.

“Don’t talk to my pet like that.”

Sans chuckled, low and deep, causing something in your stomach to twist. It felt almost like an animal instinct, a fear rooted in your gut. You turned around to look at the other monsters, but the restaurant was deserted now. The last person had closed the door behind them, meaning there was nothing stopping you from leaving. You glanced once more at the monsters fighting near the bar before you turned tail and ran. You made it to the door in a step or two and in a moment you had it pulled open. The icy air hit you hard, the change in temperature was so drastic you immediately wanted to go back inside. You couldn’t, though, not unless you wanted to play pet for a couple of dangerous monsters. You could hear them calling after you and your heart was pounding in your chest as you dashed left, hopefully towards an exit. The snow was soft beneath your feet and you slipped, the ground hitting you hard when you collided with it. You tried to scramble to your feet, but the weight that had filled the air in the restaurant hit you. You were pushed back to the ground, followed by the same low chuckle that twisted your gut.

“You’re slippery, aint’cha?” Sans said. He walked over slowly and pressed a foot in the middle of your back. He was heavy, and the pressure made your spine ache. You let out a whimper.

“Sorry, what was that?” he asked.

“Please…let me go…” you whispered. He laughed again.

“Now why should I do that? You’re lucky I don’t feel like cleaning up the mess, or I’d just kill you here and now.” His foot dug into you and you felt the air being pushed from your lungs. Then, the pressure was gone and Sans was in the snow a few feet from you. You flipped over and Grillby was standing above you, arm outstretched. You took the hand and he pulled you up. For one blissful moment you thought he was going to let you go, but one look at him told you that was nothing but a vain wish. Once you were on your feet his hand moved to your neck, gripping you solidly. You tried to swallow past his fingers, but it was difficult. Sans groaned as he got back on his feet and brushed himself off.

“You’ll regret that, Grillby.”

Grillby was still holding tight to your throat, squeezing hard as he brought his face close to yours. His hand was hot, but not alarmingly so, and his head was casting warmth over your chilled skin. Your flesh was tingling as he opened his mouth, showing sharp, tooth-like fire illuminated by a deep red from inside his being. He smelled like burning wood when he breathed on you.

“I can’t have you running away like that. It seems I might have to break you if I’m to keep you.” he said. Shivers ran down your spine and something told you it had nothing to do with the cold air. Fear coursed through your veins, but so did something else. A desire that burned through you hotter than his hand. It sounded dangerous, painful, but a desperate part of you wanted him to break you. Your heartbeat sped up as you tried to push away the thought. Grillby smiled and your heart flipped into your throat.

“That excites you, doesn’t it?”

“Wow, seriously?” Sans laughed. He was still standing a few feet away. Grillby picked you up by the neck and moved you the dozen feet over to the bar. You thought he might take you inside, but instead he pressed you up against the exterior. The brick scraped against your cold skin and you shivered. Grillby was still smiling as his hand pushed harder against your throat. It wasn’t hard enough to constrict your breath before, but now you struggled to pull a breath through your lungs as his fingers dug harder into your skin. The heat coming from him was increasing, or maybe that was just your imagination. Your pulse was throbbing and you could hear it in your ears as he leaned down to your neck. Something that must have been a tongue slid along your throat, hot and wet. It left a tingling trail over your soft skin. The heat was starting to hurt but you couldn’t manage to push a word past his fingers and as your head became more and more foggy, you lost the ability to fight back.

“Woah, Grillbz, don’t kill ‘em yet.” Sans said, shoving the bartender to the side. The fire man hissed as the skeleton replaced his position on you. The cold bones brushed over the sensitive spots on your neck and you whined.

“Looks like he burned you real good here.” Sans made a tsk-ing noise as he ran his hand gently over the burns. His eye was still glowing red and he opened his mouth, revealing a set of sharp teeth and a glowing red tongue. You felt that same desire pooling in your gut as you looked at it. He grinned when he saw your expression. “You’re kind of a freak, aint’cha?” he asked. While Grillby had been forceful, his touch was still gentle. Sans’, on the other hand, was rough, and he pushed your head to the side, exposing your neck.

“Maybe I should kiss these better, “ he mumbled as his tongue slid over the place where Grillby’s had been. The cool appendage was refreshing on the sore burns and you let out a soft sigh at the relief. His left hand was occupied with holding you down, and his right one began exploring your body. You hadn’t fallen down with a jacket, so his hand skimmed over the top of your t-shirt, resting gently on your breast. He ran a thumb over it and squeezed, listening for the sounds you made. You bit your lip as he brushed your nipple. He chuckled and slipped a hand under your shirt, sending lines of chills over your side. It moved up to your bra and slid underneath it, pressing against your bare breast. His mouth was moving on your shoulder, licking and kissing along your collarbone. Then, he bit down, and you cried out. His teeth were sharp and they sunk into the flesh easily. The pain coursed through you, but with his other hand moving over you and kneading the pain almost heightened the pleasure. Your cry turned into a soft moan and Sans released his bite on your shoulder. You looked over at him, head throbbing when you realized the blood on his mouth was yours. Grillby was standing nearby, arms crossed.

“See, Grillbz? They like playing with me more. Maybe I should just take them home with me.” Sans said. Your pulse skipped when he said that and heat was still coursing through your veins despite the temperature outside. The bite in your shoulder was throbbing and a part of you, a seemingly large part, didn’t want this to stop. Your breath was shaky and you could see it escaping in small clouds. Sans was still idly rubbing your breast and you jumped a little whenever he pinched at your nipple. Soon, though, his hand was trailing down to your pants, dancing along the waistband before sinking to beneath your legs. His bones were cold and the temperature surprised you, but his fingers were rubbing the outside of your folds and you quickly stopped caring. You wiggled your hips against his hand hoping he would give you a little more, but instead he pulled away.

“Nope. Bad pets don’t get rewards.” His hand was tight on your neck again as his eye flashed. There was something hard pressed against your leg and you swallowed. He let you move your head to look down. You weren’t quite sure what kind of magic he used, but somehow he had materialized a dick in the same fashion he had a tongue. It was large, though not shaped exactly like a human one, and it didn’t look completely solid. You reached out a hand to touch it, letting your fingers rest on the soft magic. It was warm, though not quite body temperature, and felt smooth like rubber. It was solid, unlike how it appeared, and you looked at Grillby, then Sans, wondering what would happen next. Before Sans could do anything, Grillby pulled you towards him, pressing his lips, or lack thereof, to yours. His mouth was warm and didn’t feel like you were kissing a person. His hands rand over your stomach and your back and his mouth moved to the shoulder where you were bitten. He ran soft kisses over the wound, the flames tickling the sensitive punctures. His hands warmed up your frozen skin and you sighed happily.

“Don’t injure my pet, Sans.” Grillby mumbled against your skin. An arm wrapped itself around your waist, pulling your lower half closer and you squeaked. His hands were hungry, tugging and pulling at the fabric of your pants until they were down to your knees. Grillby released you for a moment, letting you sink into the feeling of Sans’ hands on your ass as he squeezed and his bones scratched you. You shivered in the cold air and the feeling of him teasing your entrance from behind. You bit your lip, wanting more, but not wanting to say it out loud. Grillby pulled you back towards him, one hand now holding his cock. It was the same dark color as his flames and it flickered like the rest of his body. You thought back to the burns on your neck and you wondered if his dick would be any different. Sans switched to his tongue, running the cool appendage over your entrance and flicking it against your clit. You moaned, letting the feeling wash over you. The bartender took advantage of this and shoved himself into your waiting mouth. It was thick and it filled your mouth to the point where you couldn’t even speak to protest. He pulled himself out and you allowed him to push back in, starting a rhythm against your head. His hands were in your hair, running through it and gripping hard whenever he hit a sweet spot. You could feel the muscles in your stomach twitch with every movement of Sans’ tongue and it made moans spill out onto Grillby.

Then, Sans pulled back, leaving you wanting. You were still trying to move on the bartender, but you also wiggled, agitated at the lack of attention. You could hear Sans chuckling behind you.

“Patience, kiddo,” he said, “by the time I’m done with you, you’ll be begging for more. You won’t ever want to leave again.”

You weren’t left waiting for long. Sans teased you with his dick, pressing just the tip in. You tried to move back, pushing yourself onto him a little, but he moved away. Your head was starting to spin. The thrusting in and out of your mouth was driving you mad and it was all you could do to keep up with Grillby’s pace. For a while it seemed easier to just let him have his way with your mouth. You wanted Sans to give it to you, to fuck you hard and fast and take you over the edge, but he clearly wanted to be in control.

“Man, Grillbz, you sure do make it hard for a guy to get off. How are they supposed to beg for me if you’re keepin’ their mouth shut?”

“Get over it.”

Sans sighed and leaned over you again, his hand scratching against your back. Your skin was alive with the feeling of their hands on you and it took all your energy not to push back onto Sans when he brought himself to your entrance again. You waited, aching for him, until he finally pushed it in and you wanted to scream. He was bigger than Grillby, though you figured that was probably because he was made of magic. It was wide and it filled you, making your stomach twinge as he pulled out and pushed back in. It hurt, the skin stretching and the muscles straining to clamp around it. The skeleton made some sort of groan, something primal and filled with pleasure as he moved in and out of you.

“God…fuck…” he mumbled, his hands gripping your ass hard as he pounded into you. He and Grillby eventually matched pace, moving in and out of you so you were filled constantly, pummeled from both sides. Your blood was on fire, Grillby’s cock was heating up as he got excited and you hoped he was close because you weren’t sure how much more you could take. You moaned around him, the vibrations spiraling through his cock and making his hands grip your hair harder. He was moaning, curled around himself as he fucked your mouth. You could feel yourself nearing the edge, about to plunge into oblivion. Both monsters continued to pound into you until finally you came, the orgasm hitting you and exhausting you. They kept going, however, and Sans’ dick pressed against the sensitive walls, rubbing them until you felt raw. Pain racked through you and you became all too aware of the stinging in your shoulder. You cried out onto Grillby as Sans held you hard and came, his warm liquid spilling out of you and onto your legs. The fire man came soon after and he kept himself pressed to you, hands held fast, as his cum filled your stomach like hot chocolate. He pulled out and you would have collapsed if he didn’t catch you. He quickly buttoned his pants and picked you up, letting you fall against him. Your muscles felt like jelly and soon he had you on the stool at the bar, Sans tagging along behind.

Your face felt hot, though you weren’t sure if it was because of embarrassment or if it was just the aftermath. Your mouth tasted like burnt toast and you smacked your lips unpleasantly. Your hips were sore and your insides felt thoroughly used. Sans leaned on the counter and you glanced at him. He still had your dried blood on his mouth and you put a hand on your shoulder. Grillby disappeared in the back.

“So.” Sans said. You turned away from him.

“What?”

“You aint so bad for a pet.”

“I’m not your pet.”

Grillby returned with some kind of jar and what looked like a milkshake. You took a small sip of the drink as he came around the bar. It was good. The sweetness helped rid your mouth of the awful burnt taste and you were thankful. You flinched when the bartender put something from the jar on you, but it was cool and helped relieve the stinging. It was some kind of cream that he spread over your bite marks and your burns on your neck and the pain lessened to a dull throb that was barely noticeable.

“Thanks,” you mumbled. Grillby nodded, taking the jar back to the other side.

“You guys aren’t going to let me leave, are you?” You asked. Sans laughed.

“Listen, kid, even if we wanted to let you leave, Papyrus would kill you as soon as you tried.”

“I could take him,” you insisted, but you knew you probably couldn’t. You had barely escaped the Ruins with your life, and then you’d only survived this far because you’d run away from every challenge that presented itself. In a straight fight with Papyrus you’d probably get mauled. You laid your head on your arms. You were stuck here at the mercy of two monsters who wanted to use you. You thought about your soreness and your aching muscles. It wasn’t really that bad, you thought, you could probably play along.

“Alright, fine. I’ll be your pet.” You sighed.

“Great. Well then, come with me. Papyrus and I have a shed all set up just in case some mongrel like you came along.”

“Absolutely not.” Grillby said. “I know how you treat your pets. They’d die by tomorrow in your ramshackle building. They can stay with me.”

Sans growled at the bartender, and the fire man hissed back. Sans sighed.

“Fine, whatever. I’m too tired to deal with this anyway.”

You looked up as Sans was pushing himself off of the bar stool. He waved as he turned to walk out the door.

“Later, Grillbz, human.” The door chimed as he opened it and walked out. You turned to Grillby who was wiping down the counter.

“So…you’re not going to kill me, right?” You asked. Grillby shook his head.

“I’m probably the best shot you have of getting out of here alive. Sans would break you in half without me around to stop him.”

“Oh.”

“But I have better self-control. I won’t kill you. Yet.”

The ‘yet’ at the end worried you, but you didn’t see what kind of choice you had. Doing what they said for now didn’t seem too bad, so you nodded. At least you’d have a place to stay that wasn’t a shed.


End file.
